The invention relates to an apparatus for producing microcomponents with component structures which are generated in a process chamber on a substrate according to the LIGA method. The invention further relates to a method for producing microcomponents with component structures in which the microcomponents are generated in provided substrates and thereafter are relieved from the enclosing material sections, such that the material sections can be etched away (stripped). The invention further relates to the use of such an apparatus and method for stripping or removing the material sections enclosing the microcomponents.
Apparatuses and methods of this kind with which microcomponents are produced for the clock industry are well known from the state of the art. Methods are frequently used here which are based on a combination of lithography and electroplating. These methods are generally well known as LIGA methods. In such a “LIGA” method, a photoresist can be applied at first to a substrate such as a wafer or the like. A negative resist with the designation SU-8 can be used as a photoresist.
The substrate can concern a silicon wafer for example which comprises a thin gold layer on its surface on which microcomponents can grow especially well. The photoresist is applied to this silicon wafer. It especially covers the gold layer and can be exposed there selectively by means of a suitable exposure system and a mask. The unexposed places of the photoresist layer are removed in a subsequent development step.
In a subsequent electroplating process, a metal such as nickel or gold can be allowed to grow on the thus prepared substrate surface, with the respective metal beginning to grow on the places stripped of the photoresist layer. Depending on the intended application, growth can be stopped when the grown metal structure grows slightly beyond the photoresist layer.
Photoresist SU-8 comes with the disadvantage that the removal of the cross-linked SU-8 structures between metal structures deposited by electroplating is currently very complex. SU-8 is based on epoxy resin which in the cross-linked state is very stable against organic and inorganic etchants. Photoresist is removed by means of currently known etchants either very slowly or in such a way that the metallic microcomponents are also attacked and thus become useless.
Mechanical removal of the photoresist from the microcomponent is not only laborious and cost-intensive, but also causes a high rejection rate due to the extremely small dimensions of the microcomponents. Some complex structural shapes cannot even be produced at all under these conditions.
Conventional plasma methods progress on the one hand very slowly and on the other hand the metal is attacked by ions and electrons. The etching process needs to be interrupted frequently because the substrates otherwise will become too hot.
In previous methods, the end of the stripping process, i.e. the removal of the photoresist, is determined on the basis of integral temperature measurement by means of emission spectroscopy, which entails very high costs. When photoresist is removed in an etching chamber in batch operations from several microcomponents on the respective substrates, it was only possible to date to recognize the start of the etching process by means of a rise in the integral process temperature and the global end of the etching process by means of the drop in the integral process temperature. It was not possible to individually monitor the individual substrates which may have differently thick layers of photoresist and thus require differently long stripping periods. It was further not possible to recognize in time whether an individual substrate will become too hot due to a bad contact to the substrate holder for example which rests on a work plate and will thus be damaged.
WO 2004/104704 A2 discloses a lithographic method for producing microcomponents. It is tried to form etching chambers in a constructional way, through which removal of SU-8 is facilitated. Several intermediate steps are added as a result of additional bonding layers, support structures, masks and exposure steps, through which construction and production of the microcomponents becomes more laborious.